Abstract
This study was conducted to characterize and explore the endophytic fungi of selected plants from the Western Himalayas for their bioactive potential. A total of 72 strains of endophytic fungi were isolated and characterized morphologically as well as on the basis of ITS1-5.8S-ITS2 ribosomal gene sequence acquisition and analyses. The fungi represented 27 genera of which two belonged to Basidiomycota, each representing a single isolate, while the rest of the isolates comprised of Ascomycetous fungi. Among the isolated strains, ten isolates could not be assigned to a genus as they displayed a maximum sequence similarity of 95% or less with taxonomically characterized organisms. Among the host plants, the conifers, Cedrus deodara, Pinus roxburgii and Abies pindrow harbored the most diverse fungi, belonging to 13 different genera, which represented almost half of the total genera isolated. Several extracts prepared from the fermented broth of these fungi demonstrated strong bioactivity against E. coli and S. aureus with the lowest IC50 of 18 μg/ml obtained with the extract of Trichophaea abundans inhabiting Pinus sp. In comparison, extracts from only three endophytes were significantly inhibitory to Candida albicans, an important fungal pathogen. Further, 24 endophytes inhibited three or more phytopathogens by at least 50% in co-culture, among a panel of seven test organisms. Extracts from 17 fungi possessed immuno-modulatory activities with five of them showing significant immune suppression as demonstrated by the in vitro lymphocyte proliferation assay. This study is an important step towards tapping the endophytic fungal diversity from the Western Himalayas and assessing their bioactive potential. Further studies on the selected endophytes may lead to the isolation of novel natural products for use in medicine, industry and agriculture.
Highlights
Microorganisms are important sources of bioactive natural products with enormous potential for the discovery of new molecules for drug discovery, industrial use and agricultural applications (Demain 1999; Keller et al 2005; Strobel 2006; Porras-Alfaro and Bayman 2011)
We describe the characterization of endophytic fungi obtained from such plants and their bioactive potential with respect to antimicrobial activity and immune modulation
Phylogenetic affinities of the endophytic fungi The acquisition of ITS1-5.8S-ITS2 sequence data and their analyses showed diverse taxonomic affinities among the isolated endophytes
Summary
Microorganisms are important sources of bioactive natural products with enormous potential for the discovery of new molecules for drug discovery, industrial use and agricultural applications (Demain 1999; Keller et al 2005; Strobel 2006; Porras-Alfaro and Bayman 2011). Natural products remain a consistent source of drug leads with more than 40% of new chemical entities (NCEs) reported from 1981 to 2005 having been derived from microorganisms More than 60% of the anticancer and 70% of the antimicrobial drugs currently in clinical use are natural products or natural product derivatives (McAlpine et al 2005). This is not surprising in the light of their evolution over millions of years in diverse ecological niches and natural habitats. Studies based on estimation of microbial populations have revealed that only about 1% of bacteria and 5% of fungi have been characterized and the rest remain unexplored for their contribution to the human welfare (Heywood 1995; Staley et al 1997)
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